From Indiana University Sheet Music Collections:

THE OLD GREY MARE (THE WHIFFLE TREE)
Frank Panella, 1915.

1. Oh! the old grey mare was
Fighting at the front,
Fighting at the front,
Fighting at the front.
The old grey mare was
Fighting at the front
Many long years ago,
Many long years ago,
Many long years ago.
The old grey mare was
Fighting at the front,
Fighting at the front,
Fighting at the front.
Oh! The old grey mare was
Fighting at the front
Many long years ago.

2. Oh! The old grey mare ain't
What she use to be,
What she use to be,
What she use to be.
The old grey mare ain't
What she use to be
Many long years ago,
Many long years ago,
Many long years ago.
Oh! The old grey mare ain't
What she use to be,
What she use to be,
What she use to be.
Oh! The old grey mare ain't
What she use to be
Many long years ago.

Similarly:
3. The old grey mare she
Kicked at the whiffle tree....

4. The old grey mare stood
Under the apple tree....

5. Oh! The old grey mare was
Burning up the track....

6. Oh! The old grey mare she
Lost a tooth or two....

7. Oh! The old grey mare she
Carried Uncle Sam....

8. Oh! The old grey mare she
Liked her applejack....

8. Oh! The old grey mare she
Chewed tobacco too....